1. Field of the Invention
The present invention relates to a thermal transfer recording medium capable of being used repeatedly and more particularly to a thermal transfer recording medium wherein a density drop caused by the increase in the number of usage thereof is small, printing with low energy can be performed and the print quality of high density and excellent resolving power is obtained.
2. Description of the Prior Art
An example of the invention of a thermal transfer recording medium intended to be used repeatedly is described in Japanese Patent Publication Open to Public Inspection No. 68253/1979. This invention employs the technology wherein resins are used to form a finely-porous layer and heat-melting ink is impregnated in the holes and clearances in the porous layer. However the technology has disadvantageous points that the density of a dye-transfer image is low, high energy is necessary to obtain dye-transfer images with high density and the edge of the printed images lacks the sharpness even if dye-transfer images with high density may be obtained owing to the high energy impressed. Even in Japanese Patent Publication Open to Public Inspection No. 105579/1980, technology similar to the foregoing is disclosed and the same disadvantage is observed therein.
Besides the foregoing, various thermal transfer recording media capable of being used repeatedly have been devised. For example, the method wherein vinyl monomer is grafted to carbon black as is disclosed in Japanese Patent Publication Open to Public Inspection No. 185195/1982 and the method wherein an interlayer for the purpose of adhesion is provided between the substrate and the ink layer (layer of heat-melting coloring agent) as is shown in Japanese Patent Publication Open to Public Inspection Nos. 36698/1982, 138984/1982, 116193/1983 and 155995/1983 are widely known. In the methods mentioned above, transference at the same time of all coloring agents same time when heated by a thermal head and each technology is effective to a certain extent but still is insufficient.